The present invention relates generally to medical devices, systems and methods, and more particularly to small, low cost, portable infusion devices and methods that are useable to achieve precise, sophisticated, and programmable flow patterns for the delivery of therapeutic liquids such as insulin to a mammalian patient. Even more particularly, the present invention is directed to a dispenser for a fluid delivery device that utilizes a shape memory element.
Today, there are numerous diseases and other physical ailments that are treated by various medicines including pharmaceuticals, nutritional formulas, biologically derived or active agents, hormonal and gene based material and other substances in both solid or liquid form. In the delivery of these medicines, it is often desirable to bypass the digestive system of a mammalian patient to avoid degradation of the active ingredients caused by the catalytic enzymes in the digestive tract and liver. Delivery of a medicine other than by way of the intestines is known as parenteral delivery. Parenteral delivery of various drugs in liquid form is often desired to enhance the effect of the substance being delivered, insuring that the unaltered medicine reaches its intended site at a significant concentration. Also, undesired side effects associated with other routes of delivery, such as systemic toxicity, can potentially be avoided.
Often, a medicine may only be available in a liquid form, or the liquid version may have desirable characteristics that cannot be achieved with solid or pill form. Delivery of liquid medicines may best be accomplished by infusing directly into the cardiovascular system via veins or arteries, into the subcutaneous tissue or directly into organs, tumors, cavities, bones or other site specific locations within the body.
Parenteral delivery of liquid medicines into the body is often accomplished by administering bolus injections using a needle and reservoir, or continuously by gravity driven dispensers or transdermal patch technologies. Bolus injections often imperfectly match the clinical needs of the patient, and usually require larger individual doses than are desired at the specific time they are given. Continuous delivery of medicine through gravity feed systems compromise the patient""s mobility and lifestyle, and limit the therapy to simplistic flow rates and profiles. Transdermal patches have special requirements of the medicine being delivered, particularly as it relates to the molecular structure, and similar to gravity feed systems, the control of the drug administration is severely limited.
Ambulatory infusion pumps have been developed for delivering liquid medicaments to a patient. These infusion devices have the ability to offer sophisticated fluid delivery profiles accomplishing bolus requirements, continuous infusion and variable flow rate delivery. These infusion capabilities usually result in better efficacy of the drug and therapy and less toxicity to the patient""s system. An example of a use of an ambulatory infusion pump is for the delivery of insulin for the treatment of diabetes mellitus. These pumps can deliver insulin on a continuous basal basis as well as a bolus basis as is disclosed in U.S. Pat. No. 4,498,843 to Schneider et al.
The ambulatory pumps often work with a reservoir to contain the liquid medicine, such as a cartridge, a syringe or an IV bag, and use electromechanical pumping or metering technology to deliver the medication to the patient via tubing from the infusion device to a needle that is inserted transcutaneously, or through the skin of the patient. The devices allow control and programming via electromechanical buttons or switches located on the housing of the device, and accessed by the patient or clinician. The devices include visual feedback via text or graphic screens, such as liquid crystal displays known as LCD""s, and may include alert or warning lights and audio or vibration signals and alarms. The device can be worn in a harness or pocket or strapped to the body of the patient.
Currently available ambulatory infusion devices are expensive, difficult to program and prepare for infusion, and tend to be bulky, heavy and very fragile. Filling these devices can be difficult and require the patient to carry both the intended medication as well as filling accessories. The devices require specialized care, maintenance, and cleaning to assure proper functionality and safety for their intended long term use. Due to the high cost of existing devices, healthcare providers limit the patient populations approved to use the devices and therapies for which the devices can be used.
Clearly, therefore, there was a need for a programmable and adjustable infusion system that is precise and reliable and can offer clinicians and patients a small, low cost, light-weight, easy-to-use alternative for parenteral delivery of liquid medicines.
In response, the applicant of the present application provided a small, low cost, light-weight, easy-to-use device for delivering liquid medicines to a patient. The device, which is described in detail in co-pending U.S. application Ser. No. 09/943,992, filed on Aug. 31, 2001, includes an exit port, a dispenser for causing fluid from a reservoir to flow to the exit port, a local processor programmed to cause a flow of fluid to the exit port based on flow instructions from a separate, remote control device, and a wireless receiver connected to the local processor for receiving the flow instructions. To reduce the size, complexity and costs of the device, the device is provided with a housing that is free of user input components, such as a keypad, for providing flow instructions to the local processor.
What are still desired are new and improved components, such as dispensers and reservoirs, for a device for delivering fluid to a patient. Preferably, the components will be simple in design, and relatively compact, lightweight, easy to manufacture and inexpensive, such that the resulting fluid delivery device can be effective, yet inexpensive and disposable.
The present invention provides a device for delivering fluid, such as insulin for example, to a patient. The device includes an exit port assembly, a reservoir including a side wall extending towards an outlet connected to the exit port assembly, and a threaded lead screw received in the reservoir and extending towards the outlet of the reservoir. A plunger is secured to the lead screw and has an outer periphery linearly slideable along the side wall of the reservoir. The plunger and the lead screw are operatively arranged such that rotation of the lead screw in a first direction causes the plunger to slide along the side wall towards the outlet of the reservoir, which in turn causes fluid within the reservoir to be dispensed to the exit port assembly.
The device also includes a dispenser having a gear secured to the lead screw, and a moveable pawl positioned for contacting teeth of the gear during reciprocating linear movement of the moveable pawl adjacent the gear in first and second opposing linear directions. The pawl and the teeth are shaped such that linear movement of the pawl past the gear in the first linear direction causes rotation of the gear in the first rotational direction, while linear movement of the pawl past the gear in the second linear direction causes no rotation of the gear.
The dispenser also includes an elongated shape memory element having a changeable length decreasing from an uncharged length to a charged length when at least one charge is applied to the shape memory element. The shape memory element is connected between the moveable pawl such that the changeable length of the shape memory element decreasing from an uncharged length to a charged length causes linear movement of the moveable pawl past the gear in one of the first and the second linear directions. The use of a shape memory element helps provide a dispenser that is simple in design, and relatively compact, lightweight, and easy to manufacture.
According to one aspect of the present invention, the shape memory element includes two-way shape memory material. According to another aspect, the shape memory element includes one-way shape memory material.
According to a further aspect, the shape memory element includes a first set of at least two elongated parallel portions. Thinner parallel portions are provided in place of a single thicker shape memory element to provide the same pulling force, but with a quicker actuation time.
The present invention provides another device for delivering fluid. The device includes an exit port assembly, a reservoir having a side wall extending towards an outlet connected to the exit port assembly, and a threaded lead screw received in the reservoir. A plunger is secured to the lead screw and has an outer periphery linearly slideable along the side wall of the reservoir. The plunger and the lead screw are operatively arranged such that rotation of the lead screw in a first direction causes the plunger to slide along the side wall towards the outlet of the reservoir. The device also includes a gear secured to the lead screw and a moveable pawl assembly having a cage coaxially arranged with respect to the lead screw about the gear. The cage is linearly movable in opposing first and second linear directions.
A first pawl extends from the cage and is biased against teeth of the gear. The first pawl and the teeth are shaped and oriented such that the first pawl rotates the gear in the first rotational direction during linear movement of the cage in the first linear direction, but causes no rotation of the gear during linear movement of the cage in the second linear direction. In addition, the first pawl prevents rotation of the gear in an opposite second rotational direction.
A second pawl extends from the cage and is biased against the teeth of the gear. The second pawl and the teeth are shaped and oriented such that the second pawl rotates the gear in the first rotational direction during linear movement of the cage in the second linear direction, but causes no rotation of the gear during linear movement of the cage in the first linear direction. In addition, the second pawl prevents rotation of the gear in the opposite second rotational direction.
According to one exemplary embodiment, at least one elongated shape memory element is connected between the cage of the moveable pawl assembly and at least one member fixed with respect to the cage, such that a changeable length of the shape memory element decreasing from an uncharged length to a charged length causes linear movement of the moveable pawl assembly with respect to the gear.
According to one aspect of the present invention, the first and the second pawls are resiliently flexible. According to another aspect, the first and the second pawls have arcuate profiles. According to a further aspect, the first pawl and the second pawl are offset with respect to a tooth pitch of the gear. The moveable pawl assembly provides very small increments of plunger advancement without requiring additional elements, such as reducing gears connected between the plunger lead screw and the pawl assembly.
The present invention provides an additional device for delivering fluid. The device includes an exit port assembly, a reservoir including a side wall extending towards an outlet connected to the exit port assembly, and a threaded lead screw received in the reservoir. A plunger is secured to the lead screw and has an outer periphery linearly slideable along the side wall of the reservoir. The plunger and the lead screw are operatively arranged such that rotation of the lead screw in a first direction causes the plunger to slide along the side wall towards the outlet of the reservoir. First and second gears are coaxially secured to the lead screw for rotation therewith. The device also includes a moveable pawl assembly including a cage movable in opposing first and second linear directions adjacent the gears. A first pawl extends from the cage and is biased against teeth of the first gear, and the first pawl and the teeth of the first gear are shaped and oriented such that the first pawl rotates the first gear in the first rotational direction during linear movement of the cage in the first linear direction, but causes no rotation of the first gear during linear movement of the cage in the second linear direction. In addition, the first pawl prevents rotation of the first gear in an opposite second rotational direction. A second pawl extends from the cage and biased against teeth of the second gear, and the second pawl and the teeth of the second gear are shaped and oriented such that the second pawl rotates the second gear in the first rotational direction during linear movement of the cage in the first linear direction, but causes no rotation of the second gear during linear movement of the cage in the second linear direction. In addition, the second pawl prevents rotation of the second gear in the opposite second rotational direction.
According to one aspect of the present invention, the first and the second pawls have the same length, and the first and the second gears are identical but are out of phase by a single tooth pitch. This arrangement provides very small increments of plunger advancement without requiring additional elements, such as reducing gears connected between the plunger lead screw and the pawl assembly.
The present invention provides a further device for delivering fluid. The device includes an exit port assembly, a reservoir including a side wall extending towards an outlet connected to the exit port assembly, and a threaded lead screw received in the reservoir. A plunger is secured to the lead screw and has an outer periphery linearly slideable along the side wall of the reservoir. The plunger and the lead screw are operatively arranged such that rotation of the lead screw in a first direction causes the plunger to slide along the side wall towards the outlet of the reservoir. A gear is coaxially secured to the lead screw for rotation therewith, and the device further includes a moveable pawl assembly having a cam pivotally mounted coaxially on the lead screw adjacent the gear for pivotal movement in opposing first and second pivotal directions about the lead screw.
A first pawl is secured to the cam and extends towards the gear, and the first pawl and teeth of the gear are shaped and oriented such that the first pawl rotates the gear in the first rotational direction during pivotal movement of the cam in the first pivotal direction, but causes no rotation of the gear during pivotal movement of the cam in the second pivotal direction. A second pawl is secured to the cam and extends towards the teeth of the gear, wherein the second pawl and the teeth of the gear are shaped and oriented such that the second pawl rotates the gear in the first rotational direction during pivotal movement of the cam in the first pivotal direction, but causes no rotation of the gear during pivotal movement of the cam in the second pivotal direction. The first and second pawls have different lengths such that pivotal movement of the cam in the first pivotal direction can produce less than a tooth pitch of gear advancement.
The present invention provides yet another device for delivering fluid. The device includes an exit port assembly, a reservoir including a side wall extending towards an outlet connected to the exit port assembly, and a threaded lead screw received in the reservoir. A plunger is secured to the lead screw and has an outer periphery linearly slideable along the side wall of the reservoir. The plunger and the lead screw are operatively arranged such that rotation of the lead screw in a first direction causes the plunger to slide along the side wall towards the outlet of the reservoir.
The device also includes a dispenser having a barrel cam coaxial secured to the lead screw for rotation therewith and including a continuous circumferential groove with helical segments having orientations extending in the first rotational direction and successively alternating between opposing first and second ends of the barrel cam. A slide is linearly movable in opposing first and second linear directions parallel with the lead screw and adjacent the gear. The slide includes a finger extending from the slide and into the circumferential groove of the barrel cam. When the finger extends into one of the helical segments, linear movement of the slide causes rotation of the barrel cam and the lead screw in the first rotational direction.
According to one aspect of the present invention, the groove of the barrel cam also includes axial segments extending axially from each of junctures between the successive helical segments towards the ends of the barrel cam. When the finger extends into one of the axial segments, linear movement of the slide causes no rotation of the barrel cam and the lead screw. The combination of helical and axial segments can be used to control the amount of rotational motion of the lead screw produced from the linear motion of the slide.
The present invention provides a further device for delivering fluid. The device includes an exit port assembly, a reservoir including a side wall extending towards an outlet connected to the exit port assembly, and a threaded lead screw received in the reservoir. A plunger is secured to the lead screw and has an outer periphery linearly slideable along the side wall of the reservoir. The plunger and the lead screw are operatively arranged such that rotation of the lead screw in a first direction causes the plunger to slide along the side wall towards the outlet of the reservoir.
The device further includes a dispenser having a crankshaft operatively connected to the lead screw such that rotation of the crankshaft in a first rotational direction of the crankshaft causes rotation of the lead screw in the first rotational direction of the lead screw. The crankshaft includes a main shaft rotatable about a longitudinal axis, at least one counter weight secured to the main shaft for rotation therewith, and at least one crank pin. The crank pin is secured to the main shaft through the counter weight and has a longitudinal axis parallel to but radially offset from the longitudinal axis of the main shaft.
At least one elongated shape memory element is connected between the crank pin and at least one member fixed with respect to the crankshaft such that the changeable length of the shape memory element decreasing from an uncharged length to a charged length causes rotation of the crankshaft.
The present invention, therefore, provides a device for delivering fluid to a patient including new and improved components, such as dispensers utilizing shape memory elements. The components are simple in design, and relatively compact, lightweight, easy to manufacture and inexpensive, such that the resulting fluid delivery device is also relatively compact, lightweight, easy to manufacture and inexpensive such that the device can be inexpensive and disposable. In particular, the new and improved components of the present invention advantageously use shape memory elements to reduce complexity and costs.